Problem: Simplify the following expression: $r = \dfrac{-t - 9}{2t - 4} \div 2$
Dividing by a number is the same as multiplying by its inverse. $r = \dfrac{-t - 9}{2t - 4} \times \dfrac{1}{2}$ When multiplying fractions, we multiply the numerators and the denominators. $r = \dfrac{(-t - 9) \times 1} {(2t - 4) \times 2}$ $r = \dfrac{-t - 9}{4t - 8}$